1. Field of the Invention
The invention relates to an audio output apparatus, more particularly to an audio output apparatus capable of suppressing pop noise.
2. Description of the Related Art
Referring to FIGS. 1a to 1d, four circuits 11, 13, 15, 17 disclosed in Taiwanese Patent No. 275312 are shown to be capable of suppressing pop noise. The circuit 11 shown in FIG. 1a includes a bipolar junction transistor (BJT) 111 for conducting pop noise to be presented at an audio output end 12 to ground in response to a control signal. The circuit 13 shown in FIG. 1b includes a diode 131 for conducting pop noise from an audio output end 14. The circuit 15 shown in FIG. 1c includes a diode 151 for conducting pop noise from an audio output end 16 to ground. The circuit 17 shown in FIG. 1d includes diodes 171, 172 for conducting pop noise from an audio output end 18.
However, since the BJT 111 and the diodes 131, 151, 171, 172 are unidirectional, they are unable to conduct pop noise with a negative voltage. Furthermore, when the BJT 111 and the diodes 131, 151, 171, 172 are conducting, higher voltage drops are present across the BJT 111 and the diodes 131, 151, 171, 172. Such voltage drops may be amplified by a reproduction device, thereby resulting in pop noise.